In order to meet the increasing demand on large bandwidth high-speed mobile access, the Third Generation Partnership Projects (3GPP) propose the standard of Long Term Evolution-Advanced (LTE-A). As to the evolution of the Long Term Evolution (LTE) system, the LTE-A keeps the core of the LTE, and expands the frequency domain and space domain by using a series of technologies to achieve the aims of improving the spectrum utilization rate and increasing the system capacity and the like.
Wireless Relay technology is one of technologies adopted in the LTE-A, aiming to extend the coverage of a cell, reduce dead zone in communications, balance load, transfer the service of hot spots, and save the transmitting power of the User Equipment (UE).
FIG. 1 is a schematic diagram illustrating the structure of an existing network using wireless relay technology, as shown in FIG. 1, some new Relay-Nodes (RNs) are added between the original base station (or referred to as Donor-eNB) and the UE, these newly-added RNs and the Donor-eNB are wirelessly connected. Wherein the radio link between the Donor-eNB and the RN is referred to as a backhaul link, and can also be represented by an interface Un; a radio link between the RN and the UE is referred to as an access link. Downlink data first reach the Donor-eNB, and then are transferred to the RN, which retransmits the downlink data to the UE, while for the uplink data, the case is opposite.
The RN has relay function of transmitting data between the RN and the Donor-eNB, as well as between the RN and the UE managed by the RN under normal working conditions. Specifically, the relay function between the Donor-eNB and the RN can include functions of obtaining system information, measuring and reporting a measuring report, switching, transmitting data by a dedicated control channel and a shared channel and the like. The RN can also manage cells under its own jurisdiction and can manage the UE in cells under normal working conditions. The relay function between the RN and the UE includes functions of sending the system information of the RN, managing the measuring process of the UE, managing the switching process of the UE, transmitting data between the RN and the UE by a control channel and a shared channel and the like.
In the backhaul link, the RN accesses the Donor-eNB as a common user equipment. The Donor-eNB configures specific parameters for the RN after a network side performs the authentication and acquires the identity of the RN, but the Donor-eNB still manages the RN like managing a common user equipment. The RN needs to comply with protocol specifications of the common user equipment in the backhaul link. When working normally, the RN provides services for multiple user equipments within its coverage, these equipments are in a connected state or an idle state. When the user equipment covered by the RN needs to transmit data, it requires transmission on Data Radio Bearer (DRB) established on the backhaul link, in order to prevent the data of the user equipment from illegal attack, the 3GPP protocol agrees to perform integrity protection on the DRB of the backhaul link. It should be noted that, before no RN is introduced into the network, only encryption algorithm, instead of integrity protection is performed on the DRB.
The existing protocol does not relate to a specific implementing method for applying the integrity protection algorithm to the DRB of the backhaul link; moreover, after the integrity protection algorithm is applied to the DRB of the backhaul link, there is a synchronization problem in the implementation process, i.e., when the established DRB which is not configured with integrity protection is reconfigured as the DRB which applies integrity protection, there is further a problem to be solved that from which data packet the integrity protection is implemented, a typical solution to the problem is to introduce a method for converting point in time, but this method needs to introduce a new point in time cell in air interface signaling, increasing the signaling overhead of the air interface.